A gas turbine engine typically includes a fan section, a compressor section, a combustor section, and a turbine section. Air entering the compressor section is compressed and delivered into the combustion section where it is mixed with fuel and ignited to generate a high-speed exhaust gas flow. The high-speed exhaust gas flow expands through the turbine section to drive the compressor and the fan section.
Gas turbine stator vane assemblies typically include a plurality of vane segments which collectively form the annular vane assembly. Each vane segment includes one or more airfoils extending between an outer platform and an inner platform. The inner and outer platforms collectively provide radial boundaries to guide core gas flow past the airfoils. Core gas flow may be defined as gas exiting the compressor passing directly through the combustor and entering the turbine.
Vane support rings support and position each vane segment radially inside of the engine diffuser case. In most instances, cooling air bled off of the fan is directed into an annular region between the diffuser case and an outer case, and a percentage of compressor air is directed in the annular region between the outer platforms and the diffuser case, and the annular region radially inside of the inner platforms.
The fan air is at a lower temperature than the compressor air, and consequently cools the diffuser case and the compressor air enclosed therein. The compressor air is at a higher pressure and lower temperature than the core gas flow which passes on to the turbine. The higher pressure compressor air prevents the hot core gas flow from escaping the core gas flow path between the platforms. The lower temperature of the compressor flow keeps the annular regions radially inside and outside of the vane segments cool relative to the core gas flow.